A new report by iSuppli once again puts major names squarely atop the North American midsize LCD TV sales heap, after significant year-over-year sales gains at the expense of lesser-known firms like Vizio and now-bankrupt Syntax-Brillian.

Last year Vizio was a surprise LCD sales leader. But during the second quarter of 2008, Samsung led the way among 30-inch to 34-inch LCD TVs with a 17.6-percent share of the North American LCD TV market, which is up significantly from 8.5 percent a year earlier. TVs with screen sizes measuring between 30 inches and 34 inches comprise 34.1 percent of the LCD market in North America.

Meanwhile, Sony came in second with a 12.8 percent share, up from just 4.9 percent a year before. Conversely, Vizio fell from a 17.3-percent share in Q2 2007 to a 6-percent share this year.

Crave's Erica Ogg reported on the trend earlier this year, writing "Both Sony and Samsung have already responded to Vizio's price pressure with lower-cost LCD TVs of their own." The response seems to have paid off, according to iSuppli analyst Riddhi Pattel.

"[One year ago], the price differential between premium and value brands was more than $500 for [the 30-inch to 34-inch] size. However, premium brands recently have introduced value line-ups at prices comparable to value brands and available across all types of retail channels."

Part of Vizio's response has been to introduce higher-end models, like the SV470XVT, a 47-inch LCD with the ballyhooed 120Hz step-up feature. But among smaller sets, the company faces a big problem: at the bottom end it can only go so low. As CNET's David Carnoy remarked, "Vizio's entry-level 32-inch LCD, which came out for $600 a year ago. It still costs $600 today."